# | -- a binary operator, often used for horizontal concatenation

• || -- a binary operator, often used for vertical concatenation

## Ways to use symbol | :

• "Expression | Expression" -- see Expression -- the class of all expressions
• "Expression | Holder" -- see Expression -- the class of all expressions
• "Expression | Thing" -- see Expression -- the class of all expressions
• "Holder | Expression" -- see Expression -- the class of all expressions
• "Holder | Holder" -- see Expression -- the class of all expressions
• "Thing | Expression" -- see Expression -- the class of all expressions
• GradedModuleMap | GradedModuleMap -- a binary operator, often used for horizontal concatenation
• Iterator | Iterator (missing documentation)
• "Array | Array" -- see List | List -- join lists, sequences or arrays
• List | List -- join lists, sequences or arrays
• "Sequence | Sequence" -- see List | List -- join lists, sequences or arrays
• Matrix | Matrix -- join matrices horizontally
• "Matrix | RingElement" -- see Matrix | Matrix -- join matrices horizontally
• "Matrix | ZZ" -- see Matrix | Matrix -- join matrices horizontally
• "RingElement | Matrix" -- see Matrix | Matrix -- join matrices horizontally
• "RingElement | RingElement" -- see Matrix | Matrix -- join matrices horizontally
• "ZZ | Matrix" -- see Matrix | Matrix -- join matrices horizontally
• Net | Net -- join strings or nets
• "String | String" -- see Net | Net -- join strings or nets
• "String | ZZ" -- see Net | Net -- join strings or nets
• "ZZ | String" -- see Net | Net -- join strings or nets
• ZZ | ZZ -- logical or

## For the programmer

The object | is .

This operator may be used as a binary operator in an expression like x|y. The user may install binary methods for handling such expressions with code such as

         X | Y := (x,y) -> ...

where X is the class of x and Y is the class of y.