[gcalctool] Make inverses of variables work (Bug #614979)

[Robert Ancell <rancell src gnome org>]

commit 268a86a5a630d287beeb85a407f852ce77914827
Author: Robert Ancell <robert ancell gmail com>
Date:   Thu Apr 8 18:49:16 2010 +1000

    Make inverses of variables work (Bug #614979)

 NEWS                     |    2 ++
 src/mp-equation-lexer.l  |    2 +-
 src/mp-equation-parser.y |   15 +++++++++++++++
 src/unittest.c           |    3 ++-
 4 files changed, 20 insertions(+), 2 deletions(-)
---
diff --git a/NEWS b/NEWS
index 3b7ddfb..193ef0a 100644
--- a/NEWS
+++ b/NEWS
@@ -28,6 +28,8 @@ Overview of changes in gcalctool 5.31.1
 
     * Mark strings for translation that were missing (Gert Kulyk, Bug #614491)
 
+    * Make inverses of variables work (Bug #614979)
+
 Overview of changes in gcalctool 5.30.0
 
     * Fix errors in variable exponents (e.g. xy²)
diff --git a/src/mp-equation-lexer.l b/src/mp-equation-lexer.l
index 91638ea..5f22ef3 100644
--- a/src/mp-equation-lexer.l
+++ b/src/mp-equation-lexer.l
@@ -64,7 +64,7 @@ DEC_NUM  {DEC}+|{DEC}*{DECIMAL}{DEC}+
 BASE_NUM {HEX}+{SUB_NUM}|{HEX}*{DECIMAL}{HEX}+{SUB_NUM}
 
 NUMBER   {DEC_NUM}|{BASE_NUM}|{FRACTION}|{DEC_NUM}{FRACTION}
-VARIABLE {WORD}|{WORD}{SUB_NUM}|{WORD}"�¹"|{GREEKS}
+VARIABLE {WORD}|{WORD}{SUB_NUM}|{GREEKS}
 
 MOD  [mM][oO][dD]
 AND  "â?§"|[aA][nN][dD]
diff --git a/src/mp-equation-parser.y b/src/mp-equation-parser.y
index 96d0fc9..c4696fb 100644
--- a/src/mp-equation-parser.y
+++ b/src/mp-equation-parser.y
@@ -114,6 +114,20 @@ static int get_function(yyscan_t yyscanner, const char *name, const MPNumber *x,
     return 1;
 }
 
+static int get_inverse_function(yyscan_t yyscanner, const char *name, const MPNumber *x, MPNumber *z)
+{
+    char *inv_name;
+    int result;
+    
+    inv_name = malloc(sizeof(char) * (strlen(name) + strlen("�¹") + 1));
+    strcpy(inv_name, name);
+    strcat(inv_name, "�¹");
+    result = get_function(yyscanner, inv_name, x, z);
+    free(inv_name);
+
+    return result;
+}
+
 static void do_not(yyscan_t yyscanner, const MPNumber *x, MPNumber *z)
 {
     if (!mp_is_overflow(x, _mp_equation_get_extra(yyscanner)->options->wordlen)) {
@@ -230,6 +244,7 @@ variable:
   term {mp_set_from_mp(&$1, &$$);}
 | tFUNCTION exp {if (!get_function(yyscanner, $1, &$2, &$$)) YYABORT; free($1);}
 | tFUNCTION tSUPNUM exp {if (!get_function(yyscanner, $1, &$3, &$$)) YYABORT; mp_xpowy_integer(&$$, $2, &$$); free($1);}
+| tFUNCTION tNSUPNUM exp {if (!get_inverse_function(yyscanner, $1, &$3, &$$)) YYABORT; mp_xpowy_integer(&$$, -$2, &$$); free($1);}
 | tVARIABLE tSUPNUM exp {set_error(yyscanner, PARSER_ERR_UNKNOWN_FUNCTION, $1); free($1); YYABORT;}
 | tSUBNUM tROOT exp {mp_root(&$3, $1, &$$);}
 | tROOT exp {mp_sqrt(&$2, &$$);}
diff --git a/src/unittest.c b/src/unittest.c
index 9a310e1..766f0f9 100644
--- a/src/unittest.c
+++ b/src/unittest.c
@@ -364,6 +364,7 @@ test_equations()
     //test("2â?»", "", PARSER_ERR_MP); // FIXME: Maybe an error in bison?
     test("2^â??1", "0.5", 0);
     test("2^(â??1)", "0.5", 0);
+    test("x�¹", "0.5", 0);
     test("â??10^2", "â??100", 0);
     test("(â??10)^2", "100", 0);
     test("â??(10^2)", "â??100", 0);
@@ -477,7 +478,7 @@ test_equations()
 
     options.angle_units = MP_GRADIANS;
     test("sin 100", "1", 0);
-  
+
     test("0 and 0", "0", 0);
     test("1 and 0", "0", 0);
     test("0 and 1", "0", 0);