114 lines
2.3 KiB
C
114 lines
2.3 KiB
C
#include "reader.h"
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#include <ctype.h>
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#include <stddef.h>
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static int parse_number(
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memory_pool_t *pool, const char *input, int len, expression_t **out)
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{
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(void)pool;
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int value = 0, used = 0;
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while (used < len && isdigit(input[used])) {
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value *= 10;
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value += input[used] - '0';
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++used;
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}
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if (0 == used)
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return 0;
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expression_t *number = allocate_expression(pool);
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number->is_number = true;
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number->number = value;
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*out = number;
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return used;
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}
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static int parse_term(
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memory_pool_t *pool, const char *input, int len, expression_t **out)
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{
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int result, used = 0;
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expression_t *expr;
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result = parse_number(pool, input, len, &expr);
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if (0 >= result)
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return 0;
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used += result;
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while (len > used) {
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const expression_t *term0 = expr;
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operator_t operator;
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if ('*' == input[used])
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operator = OPERATOR_MULTIPLY;
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else if ('/' == input[used])
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operator = OPERATOR_DIVIDE;
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else
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break;
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++used;
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expression_t *term1;
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result = parse_number(pool, input + used, len - used, &term1);
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if (0 >= result)
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return 0;
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used += result;
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expr = allocate_expression(pool);
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expr->is_number = false;
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expr->application.operator= operator;
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expr->application.operands[0] = term0;
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expr->application.operands[1] = term1;
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}
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*out = expr;
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return used;
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}
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static int parse_expression(
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memory_pool_t *pool, const char *input, int len, expression_t **out)
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{
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int result, used = 0;
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expression_t *expr;
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result = parse_term(pool, input, len, &expr);
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if (0 >= result)
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return 0;
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used += result;
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while (len > used) {
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const expression_t *term0 = expr;
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operator_t operator;
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if ('+' == input[used])
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operator = OPERATOR_ADD;
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else if ('-' == input[used])
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operator = OPERATOR_SUBTRACT;
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else
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break;
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++used;
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expression_t *term1;
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result = parse_term(pool, input + used, len - used, &term1);
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if (0 >= result)
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return 0;
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used += result;
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expr = allocate_expression(pool);
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expr->is_number = false;
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expr->application.operator= operator;
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expr->application.operands[0] = term0;
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expr->application.operands[1] = term1;
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}
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*out = expr;
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return used;
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}
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const expression_t *
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read_expression(memory_pool_t *pool, const char *input, int len)
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{
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expression_t *expression;
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parse_expression(pool, input, len, &expression);
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return expression;
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}
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