| unaryOp | Language.Egison.Primitives.Utils |
| UnboundVariable | |
| 1 (Data Constructor) | Language.Egison.Type.Error, Language.Egison.Type |
| 2 (Data Constructor) | Language.Egison.Data, Language.Egison |
| UnboundVariableWarning | Language.Egison.Type.Error, Language.Egison.Type |
| unconsCollection | Language.Egison.Data.Collection |
| Undefined | Language.Egison.Data, Language.Egison |
| UndefinedExpr | Language.Egison.AST, Language.Egison.IExpr, Language.Egison |
| UnificationError | Language.Egison.Type.Error, Language.Egison.Type |
| unify | Language.Egison.Type.Unify |
| UnifyError | Language.Egison.Type.Unify |
| unifyMany | Language.Egison.Type.Unify |
| unifyStrict | Language.Egison.Type.Unify |
| unifyStrictWithConstraints | Language.Egison.Type.Unify |
| unifyTypes | Language.Egison.Type.Infer, Language.Egison.Type |
| unifyWithConstraints | Language.Egison.Type.Unify |
| unifyWithTopLevel | Language.Egison.Type.Unify |
| unPatternTypeEnv | Language.Egison.Type.Env |
| unsnocCollection | Language.Egison.Data.Collection |
| unSubst | Language.Egison.Type.Subst |
| UnsupportedExpressionWarning | Language.Egison.Type.Error, Language.Egison.Type |
| UnsupportedFeature | Language.Egison.Type.Error, Language.Egison.Type |
| unTypeEnv | Language.Egison.Type.Env |
| updateHash | Language.Egison.Data.Utils |
| upperReservedWords | Language.Egison.Parser.NonS |
| User | Language.Egison.IExpr |
| UserMatcher | Language.Egison.Data, Language.Egison |
| UserrefsExpr | Language.Egison.AST, Language.Egison |
| Userscript | Language.Egison.AST, Language.Egison |