fix gcc 10 compilation issue #24
- non-const lambdas defined in a header have external linkage
- so if two compilation units include them get 'multiple definition' errors (at least with gcc 10)
- put lambdas defined in a header file inside anonymous namespace to resolve this
- resolves #24 (closed)
Closes #24 (closed)
Edited by Santiago Ospina De Los Ríos