[poincare] Add a Logarithm expression

Change-Id: Iaf10dec4b298811edaef1cebd04ac0b0175d9025

poincare/Makefile

@@ -16,6 +16,7 @@ objs += $(addprefix poincare/src/,\
   function.o\
   integer.o\
   leaf_expression.o\
+  logarithm.o\
   power.o\
   product.o\
   sine.o\

poincare/include/poincare.h

@@ -9,6 +9,7 @@
 #include <poincare/fraction.h>
 #include <poincare/function.h>
 #include <poincare/integer.h>
+#include <poincare/logarithm.h>
 #include <poincare/power.h>
 #include <poincare/product.h>
 #include <poincare/sine.h>

poincare/include/poincare/expression.h

@@ -13,7 +13,7 @@ class Expression {
       Cosine,
       Float,
       Integer,
-      Log,
+      Logarithm,
       Fraction,
       Power,
       Product,

poincare/include/poincare/logarithm.h

@@ -0,0 +1,15 @@
+#ifndef POINCARE_LOGARITHM_H
+#define POINCARE_LOGARITHM_H
+
+#include <poincare/function.h>
+
+class Logarithm : public Function {
+public:
+  Logarithm();
+  float approximate(Context & context) const override;
+  Type type() const override;
+  Expression * cloneWithDifferentOperands(Expression ** newOperands,
+      int numberOfOperands, bool cloneOperands = true) const override;
+};
+
+#endif

poincare/src/expression_lexer.l

@@ -70,6 +70,7 @@
 sin { poincare_expression_yylval.expression = new Sine(); return FUNCTION; }
 cos { poincare_expression_yylval.expression = new Cosine(); return FUNCTION; }
 tan { poincare_expression_yylval.expression = new Tangent(); return FUNCTION; }
+log { poincare_expression_yylval.expression = new Logarithm(); return FUNCTION; }
 [A-Za-z]+ { poincare_expression_yylval.string = yytext; return(SYMBOL); }
 \+ { return(PLUS); }
 \- { return(MINUS); }

poincare/src/logarithm.cpp

@@ -0,0 +1,28 @@
+#include <poincare/logarithm.h>
+
+extern "C" {
+#include <assert.h>
+#include <math.h>
+}
+
+Logarithm::Logarithm() :
+  Function("log")
+{
+}
+
+Expression::Type Logarithm::type() const {
+  return Expression::Type::Logarithm;
+}
+
+Expression * Logarithm::cloneWithDifferentOperands(Expression** newOperands,
+        int numberOfOperands, bool cloneOperands) const {
+  assert(numberOfOperands == 1);
+  assert(newOperands != nullptr);
+  Logarithm * c = new Logarithm();
+  c->setArgument(*newOperands, cloneOperands);
+  return c;
+}
+
+float Logarithm::approximate(Context& context) const {
+  return log10f(m_arg->approximate(context));
+}