[poincare/parser] Use infinity symbol

- Use infinity symbol
- Parse inf, oo, infity

poincare/include/poincare/infinity.h

@@ -56,7 +56,7 @@ public:
   static Infinity Builder(bool negative);
   Expression setSign(ExpressionNode::Sign s);
   static const char * Name() {
-    return "inf";
+    return "∞";
   }
   static int NameSize() {
     return 4;

poincare/src/parsing/parser.cpp

@@ -44,6 +44,9 @@ bool Parser::IsSpecialIdentifierName(const char * name, size_t nameLength) {
   return (
     Token::CompareNonNullTerminatedName(name, nameLength, Symbol::k_ans)     == 0 ||
     Token::CompareNonNullTerminatedName(name, nameLength, Infinity::Name())  == 0 ||
+    Token::CompareNonNullTerminatedName(name, nameLength, "inf")             == 0 ||
+    Token::CompareNonNullTerminatedName(name, nameLength, "infinity")        == 0 ||
+    Token::CompareNonNullTerminatedName(name, nameLength, "oo")              == 0 ||
     Token::CompareNonNullTerminatedName(name, nameLength, Undefined::Name()) == 0 ||
     Token::CompareNonNullTerminatedName(name, nameLength, Unreal::Name())    == 0 ||
     Token::CompareNonNullTerminatedName(name, nameLength, "u")               == 0 ||
@@ -426,7 +429,14 @@ void Parser::parseSequence(Expression & leftHandSide, const char * name, Token::
 void Parser::parseSpecialIdentifier(Expression & leftHandSide) {
   if (m_currentToken.compareTo(Symbol::k_ans) == 0) {
     leftHandSide = Symbol::Ans();
-  } else if (m_currentToken.compareTo(Infinity::Name()) == 0) {
+  } else if (m_currentToken.compareTo(Infinity::Name()) == 0 ||
+             m_currentToken.compareTo("inf")            == 0 ||
+             m_currentToken.compareTo("infinity")       == 0 ||
+             m_currentToken.compareTo("oo")             == 0
+    ) {
+
+    leftHandSide = Infinity::Builder(false);
+  } else if (m_currentToken.compareTo("inf") == 0) {
     leftHandSide = Infinity::Builder(false);
   } else if (m_currentToken.compareTo(Undefined::Name()) == 0) {
     leftHandSide = Undefined::Builder();

poincare/src/parsing/tokenizer.cpp

@@ -224,7 +224,7 @@ Token Tokenizer::popToken() {
   if (c == '}') {
     return Token(Token::RightBrace);
   }
-  if (c == UCodePointSquareRoot) {
+  if (c == UCodePointSquareRoot || c == UCodePointInfinity) {
     Token result(Token::Identifier);
     result.setString(start, UTF8Decoder::CharSizeOfCodePoint(c));
     return result;