diff --git a/kmath-ast/reference/ArithmeticsEvaluator.g4 b/kmath-ast/reference/ArithmeticsEvaluator.g4
index 137d42860..ba8166bc8 100644
--- a/kmath-ast/reference/ArithmeticsEvaluator.g4
+++ b/kmath-ast/reference/ArithmeticsEvaluator.g4
@@ -2,11 +2,11 @@ grammar ArithmeticsEvaluator;
 
 fragment DIGIT: '0'..'9';
 fragment LETTER: 'a'..'z';
-fragment CAPITAL_LETTER: 'A'..'Z'
+fragment CAPITAL_LETTER: 'A'..'Z';
 fragment UNDERSCORE: '_';
 
 ID: (LETTER | UNDERSCORE | CAPITAL_LETTER) (LETTER | UNDERSCORE | DIGIT | CAPITAL_LETTER)*;
-NUM: (DIGIT | '.')+ ([eE] MINUS? DIGIT+)?;
+NUM: (DIGIT | '.')+ ([eE] (MINUS? | PLUS?) DIGIT+)?;
 MUL: '*';
 DIV: '/';
 PLUS: '+';
@@ -17,7 +17,7 @@ LPAR: '(';
 RPAR: ')';
 WS: [ \n\t\r]+ -> skip;
 
-number
+num
     : NUM
     ;
 
@@ -34,7 +34,7 @@ binaryFunction
     ;
 
 term
-    : number
+    : num
     | singular
     | unaryFunction
     | binaryFunction
diff --git a/kmath-ast/src/commonMain/kotlin/scientifik/kmath/ast/parser.kt b/kmath-ast/src/commonMain/kotlin/scientifik/kmath/ast/parser.kt
index 27f133d6a..a0b729ffe 100644
--- a/kmath-ast/src/commonMain/kotlin/scientifik/kmath/ast/parser.kt
+++ b/kmath-ast/src/commonMain/kotlin/scientifik/kmath/ast/parser.kt
@@ -18,7 +18,7 @@ import scientifik.kmath.operations.SpaceOperations
  * TODO move to common
  */
 object ArithmeticsEvaluator : Grammar<MST>() {
-    private val num: Token by token("[\\d.]+(?:[eE]-?\\d+)?".toRegex())
+    private val num: Token by token("[\\d.]+(?:[eE][-+]?\\d+)?".toRegex())
     private val id: Token by token("[a-z_A-Z][\\da-z_A-Z]*".toRegex())
     private val lpar: Token by token("\\(".toRegex())
     private val rpar: Token by token("\\)".toRegex())