k&r 04-06: added variable support
Tibor Bizjak
parent
c1b83c5cd4
commit
9aa5c11369
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@ -2,6 +2,8 @@
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#include <stdlib.h>
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#include <string.h>
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#include <math.h>
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#include <ctype.h>
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#include <assert.h>
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/* --------- ERROR MESSAGES */
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#define printerr(format, ...) printf("error: " format "\n", ##__VA_ARGS__)
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@ -12,6 +14,7 @@
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#define EMPTY_STACK_ERR "stack empty"
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#define SHORT_STACK_ERR "not enough elements on stack"
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#define UNKNOWN_TOKEN_ERR "unknown token %s"
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#define VAR_NOT_SET_ERR "variable %c has no value"
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/* --------- PROMPT FORMATS */
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#define PROMPT_F ">> "
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@ -28,6 +31,7 @@
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int sp = 0;
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double val[MAXVAL];
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/* length: current length of stack */
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#define length() sp
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/* push: push f onto value stack */
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#define push(x) ((sp < MAXVAL) ? val[sp++] = (x) : printerr(FULL_STACK_ERR, ((double) (x))))
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@ -37,8 +41,6 @@ double val[MAXVAL];
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#define peek() (sp ? val[sp-1] : (printerr(EMPTY_STACK_ERR), 0))
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/* clear: clear stack */
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#define clear() (sp = 0)
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/* print_peek: print top element, leave stack unchanged */
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#define print_peek() printf(PEEK_PRINT_F, peek())
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/* dup: duplicate top element */
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#define dup() push(peek())
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/* swap: swap top two elements */
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@ -49,6 +51,38 @@ double val[MAXVAL];
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} \
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} while (0)
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/* -------- STACK PRINTING FUNCTIONS */
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double lst_print;
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/* print_peek: print top element, leave stack unchanged */
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#define print_peek() printf(PEEK_PRINT_F, lst_print = peek())
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/* print_pop: pop top element and print it */
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#define print_pop() printf(POP_PRINT_F, lst_print = pop())
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/* ------- GLOBAL VARIABLE NAMESPACE */
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#define NS_SIZE ('z' - 'a' + 1)
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char var_flags[NS_SIZE];
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double var_vals[NS_SIZE];
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/* set_var: pop val from stack, set variable c to val */
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#define set_var(c) \
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do { \
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int i = c - 'a'; \
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var_flags[i] = 1; \
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var_vals[i] = pop(); \
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} while (0)
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/* get_var: push value of c to stack */
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#define get_var(c) \
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do { \
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int i = c - 'a'; \
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if (!var_flags[i]) \
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printerr(VAR_NOT_SET_ERR, i+'a'); \
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else \
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push(var_vals[i]); \
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} while (0)
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/* --------- CALCULATOR FUNCTION TYPES */
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/* the following macros allow us to call native c constructs in a declarative style */
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@ -88,11 +122,13 @@ double val[MAXVAL];
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void help(void);
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#define COMMANDS \
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X(_, "last printed value", CALL, lst_print, VALUE) \
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X(ENTER, "pop top of stack and print it", CALL, print_pop, COMMAND) \
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X(print, "print top of stack", CALL, print_peek, COMMAND) \
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X(dup, "duplicate top of stack", COMMAND) \
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X(swap, "swap top two elements of stack", COMMAND) \
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X(clear, "clear stack", COMMAND) \
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X(help, "print all available commands", COMMAND)
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X(help, "print all available commands", COMMAND) \
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#define OPERATORS \
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X(+, "add operands", COMM_OP) \
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@ -103,7 +139,8 @@ void help(void);
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X(>, "greater than", NONC_OP, double) \
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X(<, "less than", NONC_OP, double) \
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X(<=, "less than or equal", NONC_OP, double) \
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X(>=, "greater than or equal", NONC_OP, double)
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X(>=, "greater than or equal", NONC_OP, double) \
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X(==, "test equality", COMM_OP)
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#define MATH_H_BINDINGS \
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X(sin, "sine", UNARY_FUN) \
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@ -132,12 +169,19 @@ void help(void);
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OPERATORS \
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MATH_H_BINDINGS
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/* variable manipulation tokens */
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#define VAR_TOKENS \
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X('=', "pop value top from stack and set %s to value", set_var) \
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X('$', "push value of %s to top of stack", get_var)
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/* --------- MAIN PROGRAM */
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#define MAXTOKEN 100
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int gettoken(char *token, int max_t);
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char * parsef(char *s, double *x);
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/* reverse Polish calculator */
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int main()
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{
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@ -149,7 +193,7 @@ int main()
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while (t_len = gettoken(token, MAXTOKEN)) {
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if (t_len < 0) { /* newline token */
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if (length())
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printf(POP_PRINT_F, pop());
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print_pop();
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printf(PROMPT_F);
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} else
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#define X(F, DESC, APPLY, ...) \
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@ -157,6 +201,12 @@ int main()
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APPLY(F, ##__VA_ARGS__); \
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else
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TOKENS
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#undef X
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#define X(C, DESC, F) \
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if (t_len == 2 && token[0] == C && isalpha(token[1])) \
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F(tolower(token[1])); \
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else
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VAR_TOKENS
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#undef X
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if (*parsef(token, &x) == '\0')
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push(x);
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@ -171,21 +221,31 @@ int main()
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return 0;
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}
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/* ---------- HELP COMMAND */
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#define MAX_CMD_W 10 /* token padding */
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#define VAR_STR "X" /* string to represent variable */
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/* we verify that no token is to large to be pretty printed */
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#define X(TOKEN, ...) \
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static_assert(sizeof(#TOKEN) / sizeof(char) <= MAX_CMD_W, \
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"size of " #TOKEN " is to large for pretty printing " \
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"in help command");
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TOKENS
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#undef X
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#define COMMAND_W "10"
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#define NEWLINE_DESC "pop top of stack and print it"
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/* help: prints all available calculator functions */
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void help(void)
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{
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printf("%-" COMMAND_W "s" NEWLINE_DESC "\n", "ENTER");
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#define X(F, DESC, ...) printf("%-" COMMAND_W "s" DESC "\n", #F);
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#define X(C, DESC, ...) \
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printf("%c%-*s" DESC "\n", C, MAX_CMD_W-1, VAR_STR, VAR_STR);
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VAR_TOKENS
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#undef X
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#define X(F, DESC, ...) printf("%-*s" DESC "\n", MAX_CMD_W, #F);
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TOKENS
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#undef X
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}
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/* -------- PARSING FUNCTIONS */
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#include <ctype.h>
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#define BLANK ' '
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/* gettoken: get next space delimited token from input
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