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87 lines
2.5 KiB
Plaintext
87 lines
2.5 KiB
Plaintext
B/numt: Number Template.
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@Purpose: Support for parsing integers.
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@-------------------------------------------------------------------------------
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@p Understanding.
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In our target virtual machines, numbers are stored in twos-complement form,
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so that a 16-bit VM can hold the range of integers $-2^{15} = -32768$ to
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$2^{15}-1 = +32767$, while a 32-bit VM can hold $-2^{31} = -2147483648$ to
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$2^{31}-1 = +2147483647$: the token below accepts exactly those ranges.
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@c
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[ DECIMAL_TOKEN wnc wna r n wa wl sign base digit digit_count original_wn group_wn;
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wnc = wn; original_wn = wn; group_wn = wn;
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{-call:Plugins::Parsing::Tokens::Values::number}
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wn = wnc;
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r = ParseTokenStopped(ELEMENTARY_TT, NUMBER_TOKEN);
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if ((r == GPR_NUMBER) && (parsed_number ~= 10000)) return r;
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wn = wnc;
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wa = WordAddress(wn);
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wl = WordLength(wn);
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sign = 1; base = 10; digit_count = 0;
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if (wa->0 ~= '-' or '$' or '0' or '1' or '2' or '3' or '4'
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or '5' or '6' or '7' or '8' or '9')
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return GPR_FAIL;
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if (wa->0 == '-') { sign = -1; wl--; wa++; }
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if (wl == 0) return GPR_FAIL;
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n = 0;
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while (wl > 0) {
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if (wa->0 >= 'a') digit = wa->0 - 'a' + 10;
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else digit = wa->0 - '0';
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digit_count++;
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switch (base) {
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2: if (digit_count == 17) return GPR_FAIL;
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10:
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#Iftrue (WORDSIZE == 2);
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if (digit_count == 6) return GPR_FAIL;
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if (digit_count == 5) {
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if (n > 3276) return GPR_FAIL;
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if (n == 3276) {
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if (sign == 1 && digit > 7) return GPR_FAIL;
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if (sign == -1 && digit > 8) return GPR_FAIL;
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}
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}
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#Ifnot; ! i.e., if (WORDSIZE == 4)
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if (digit_count == 11) return GPR_FAIL;
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if (digit_count == 10) {
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if (n > 214748364) return GPR_FAIL;
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if (n == 214748364) {
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if (sign == 1 && digit > 7) return GPR_FAIL;
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if (sign == -1 && digit > 8) return GPR_FAIL;
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}
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}
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#Endif;
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16: if (digit_count == 5) return GPR_FAIL;
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}
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if (digit >= 0 && digit < base) n = base*n + digit;
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else return GPR_FAIL;
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wl--; wa++;
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}
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parsed_number = n*sign; wn++;
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return GPR_NUMBER;
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];
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@p Truth states.
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And although truth states are not strictly speaking numbers, this seems as
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good a point as any to parse them:
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@c
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[ TRUTH_STATE_TOKEN original_wn wd;
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original_wn = wn;
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{-call:Plugins::Parsing::Tokens::Values::truth_state}
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wn = original_wn;
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wd = NextWordStopped();
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if (wd == 'true') { parsed_number = 1; return GPR_NUMBER; }
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if (wd == 'false') { parsed_number = 0; return GPR_NUMBER; }
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wn = original_wn;
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return GPR_FAIL;
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];
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@p Absolute value.
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It's convenient to have this around somewhere:
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@c
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[ NUMBER_TY_Abs x; if (x<0) return -x; return x; ];
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