Update installation instructions

doc/src/installation.md

@@ -1,54 +1,44 @@
 # Installation
 
-## Dependencies
+## From a Tarball Using Pip
 
-End users (and distributions) are encouraged to use the tarball, which only
-depends on Python and a few Python packages (`llvmlite`, `pytest`,
-`prompt_toolkit` and `antlr4-python3-runtime`). The LFortran standard library
-needs to be compiled and it needs a C compiler. Down the road (see our
-[roadmap](index.md)), LFortran will be gradually rewritten in C++, so it will
-also depend on a C++ compiler.
-
-The tarball is generated automatically by our CI (continuous integration) and
-contains some autogenerated files: the parser, which is generated by ANTLR4
-(requires Java) and the AST and ASR nodes, which is generated by an ASDL
-translator (requires Python). The Java requirement is only needed when using
-git directly, the tarball does not depend on Java in any way.
-
-## From a Tarball
-
-This is the easiest way.
-Download the latest tarball from
-[https://lfortran.org/download/](https://lfortran.org/download/).
-
-Install prerequisites and LFortran (works on Linux, macOS and Windows):
+The easiest way is to simply `pip` install LFortran. An example:
 ```bash
-conda create -n lfortran python=3.7 pytest llvmlite prompt_toolkit cmake make
+conda create -n lfortran python=3.7
 conda activate lfortran
-pip install antlr4-python3-runtime scikit-build
-wget https://lfortran.github.io/tarballs/release/lfortran-0.1.12.tar.gz
-tar xzf lfortran-0.1.12.tar.gz
-cd lfortran-0.1.12
-pip install .
+pip install lfortran
 ```
+This works on Linux, macOS and Windows. Pip will automatically download all
+build and run time dependencies, compile and install LFortran. The only
+prerequisite that you have to have is a working C compiler.
+
 Now the `lfortran` environment has the `lfort` compiler available, you can
 start the interactive prompt by executing `lfort`, or see the command line
 options using `lfort -h`.
 
-Note: besides the above prerequisites installed by `conda`, you also have to
-have a C compiler.
-
-Note on macOS: if `wget` is not present, use `curl -O` instead.
-
 Optional: run tests:
 ```bash
 pytest --pyargs lfortran
 ```
 
+You can also install any tarball from
+[https://lfortran.org/download/](https://lfortran.org/download/) directly,
+e.g.:
+```bash
+pip install https://lfortran.github.io/tarballs/release/lfortran-0.1.14.tar.gz
+```
+or equivalently by:
+```bash
+wget https://lfortran.github.io/tarballs/release/lfortran-0.1.14.tar.gz
+tar xzf lfortran-0.1.14.tar.gz
+cd lfortran-0.1.14
+pip install .
+```
+
 
 ## From Git
 
-This works both on Linux, macOS and Windows:
+This works on Linux, macOS and Windows:
 ```bash
 conda create -n lfortran python=3.7 pytest llvmlite prompt_toolkit cmake make
 conda activate lfortran
@@ -58,6 +48,11 @@ Install Java and then ANTLR, say, into `~/ext`:
 ```bash
 export CLASSPATH="$HOME/ext/antlr-4.7-complete.jar:$CLASSPATH"
 ```
+Clone the LFortran git repository:
+```
+git clone https://gitlab.com/lfortran/lfortran
+cd lfortran
+```
 Build:
 ```bash
 ./build.sh
@@ -70,3 +65,21 @@ Run an interactive prompt:
 ```bash
 ./lfort
 ```
+
+## Note About Dependencies
+
+End users (and distributions) are encouraged to use the tarball
+from [https://lfortran.org/download/](https://lfortran.org/download/),
+which only depends on Python and a few Python packages (`llvmlite`, `pytest`,
+`prompt_toolkit` and `antlr4-python3-runtime`). The LFortran standard library
+needs to be compiled and it needs a C compiler. Down the road (see our
+[roadmap](index.md)), LFortran will be gradually rewritten in C++, so it will
+also depend on a C++ compiler.
+
+The tarball is generated automatically by our CI (continuous integration) and
+contains some autogenerated files: the parser, which is generated by ANTLR4
+(requires Java) and the AST and ASR nodes, which is generated by an ASDL
+translator (requires Python). The Java requirement is only needed when using
+git directly, the tarball does not depend on Java in any way.
+
+The same tarball is accessible from our Downloads page as well as from PyPI.